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Cumulative Preferred Stock (Details) - CAD ($) $ / shares in Units, $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2013
Class of Stock [Line Items] |  |  |
Preferred Stock, Shares Outstanding | 41,000,000 | 29,000,000 |
Proceeds From Issuance Of Preferred Stock And Preference Stock Net | $ 295 |  |
Series A Preferred Stock [Member] |  |  |
Class of Stock [Line Items] |  |  |
Preferred Stock, Dividends Per Share, Declared | $ 0.6388 |  |
Preferred Stock, Redemption Price Per Share | $ 25 |  |
Preferred stock, dividend rate, percentage | 4.40% |  |
Preferred Stock, Shares Outstanding | 3,864,636 | 3,864,636 |
Proceeds From Issuance Of Preferred Stock And Preference Stock Net | $ 95 | $ 95 |
Series B Preferred Stock [Member] |  |  |
Class of Stock [Line Items] |  |  |
Preferred Stock, Redemption Price Per Share | $ 25 |  |
Preferred stock, dividend rate, percentage | 2.393% |  |
Preferred Stock, Shares Outstanding | 2,135,364 | 2,135,364 |
Proceeds From Issuance Of Preferred Stock And Preference Stock Net | $ 52 | $ 52 |
Series C Preferred Stock [Member] |  |  |
Class of Stock [Line Items] |  |  |
Preferred Stock, Dividends Per Share, Declared | $ 1.1802 |  | $ 1.025
Preferred Stock, Redemption Price Per Share | $ 25 |  |
Preferred stock, dividend rate, percentage | 4.10% |  |
Preferred Stock, Shares Outstanding | 10,000,000 | 10,000,000 |
Proceeds From Issuance Of Preferred Stock And Preference Stock Net | $ 245 | $ 245 |
Series E Preferred Stock [Member] |  |  |
Class of Stock [Line Items] |  |  |
Preferred Stock, Dividends Per Share, Declared | $ 1.125 |  |
Preferred Stock, Redemption Price Per Share | $ 26 |  |
Preferred stock, dividend rate, percentage | 4.50% |  |
Preferred Stock, Shares Outstanding | 5,000,000 | 5,000,000 |
Proceeds From Issuance Of Preferred Stock And Preference Stock Net | $ 122 | $ 122 |
Series F Preferred Stock [Member] |  |  |
Class of Stock [Line Items] |  |  |
Preferred Stock, Dividends Per Share, Declared | $ 1.0625 |  |
Preferred Stock, Redemption Price Per Share | $ 25 |  |
Preferred stock, dividend rate, percentage | 4.25% |  |
Preferred Stock, Shares Outstanding | 8,000,000 | 8,000,000 |
Proceeds From Issuance Of Preferred Stock And Preference Stock Net | $ 195 | $ 195 |
Series H Preferred Stock [Member} |  |  |
Class of Stock [Line Items] |  |  |
Preferred Stock, Dividends Per Share, Declared | $ 1.225 |  |
Preferred Stock, Redemption Price Per Share | $ 25 |  |
Preferred stock, dividend rate, percentage | 4.90% |  |
Preferred Stock, Shares Outstanding | 12,000,000 |  |
Proceeds From Issuance Of Preferred Stock And Preference Stock Net | $ 295 | $ 0 |

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- Definition The price per share at which the preferred stock of an entity that has priority over common stock in the distribution of dividends and in the event of liquidation of the entity is redeemed or may be called at. The redemption features of this preferred stock are solely within the control of the issuer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21475-112644 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21564-112644 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21488-112644 + Details
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